The present invention relates to lubricating means or cooling means for moveable machine parts within a housing having a sump containing a fluid and a rotatable shaft and in particular to lubricating means for supplying bearings and other relatively moveable machine parts of a power unit with lubricant or coolant under pressure.
It is well known in the art that lubrication of transmission gears and bearing members in power transmission units is partially provided for by having certain of the gears rotated within the lubricant contained in the lubricant sump located in the bottom of the housing. While this system is helpful to supply lubricants to the various gears and bearings and moving machine parts, it is generally required to use, in addition, a positive-type pump to provide forced lubrication to various moveable machine parts within the housing in conjunction with the conventional splash feed system. The positive-type pumps are expensive, require considerable power to operate and require a considerable space in the housing unit where space is valuable, thus adding additional cost, requiring additional power and absorbing a space that could be used for other components.
Some prior art systems have attempted to overcome these problems by providing a pitot type tube pump for circulating lubricant through a power transmission under pressure by providing a lubricant receiving chamber on one of the power transmission gears and providing the chambers with lubricant whenever the gears rotate. When the gears rotate to a certain position, the intake nozzle of a pitot tube receives the lubricant from the chambers and forces it under pressure from the pitot tube to a distribution chamber which is in fluid communication with various passageways leading to the bearings and other moving parts of the transmission requiring lubrication. This system is found, for example, in U.S. Pat. No. 3,065,822. In this device, the power transmission gear having the lubricant receiving chamber is fixedly attached to the power shaft and is driven at whatever rate the shaft is turning. Thus, a direct driven gear is required which takes up space, is expensive and uses considerable power because it is directly driven from the power train. In addition, the speed of the gear, and thus the pressure, varies with a change in speed of the transmission.
In prior art U.S. Pat. No. 1,466,731, the ring is driven by the use of a well known shear area causing a frictional drag between the ring and the shaft. In this patent the oil ring is L-shaped with a very small, localized, shear area on the end of one leg of the L. This is a very low power drive and would not provide enough horsepower to activate any useful pump. Thus, a separate shaft driven impeller is required.
One important advantage of the axial shear drive is that the speed of the ring is proportional to the square root of the main shaft speed. This is an important advantage where the main shaft varies in speed. With the shear drive arrangement, the oil pumping system provides more nearly constant output than a system whose speed is directly varied with the main shaft speed.
Another major advantage of the use of an axial shear drive with the present invention is the ability to adjust the power transmitted to the ring by changing the axial gap between the ring and the drive sheave. This allows relatively large powers to be transmitted, in the 1 to 10 horsepower range.
Further, the present invention compensates for variation in horsepower transmitted to the oil ring from the drive sheave due to the change in viscosity of the lube oil due to temperature changes. This is accomplished by using metals with dissimilar coefficients of thermal expansion to change the axial gap between the ring and the drive sheave in response to temperature. It has been found that where a fixed gap exists with no compensation for thermal expansion of the ring and drive sheave, the power transmitted due to temperature change can vary through a 10 to 1 variation.
If the axial gap between the ring and the drive sheave is corrected for thermal expansion due to temperature by the use of dissimilar metals, a power variation of 3 to 1 is obtained. By using an additional correction as taught by the present invention, the power transmitted to the ring is relatively constant during a temperature range of 30.degree. F. to 200.degree. F.